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Turbo AFM or MAF kit

scam75

scam75

Well-known member
Hello all.

Car is running lean, I'm pretty certain its the SciVision loom, I did manage to make it slightly worse by changing over the MAF sensor to see if that was the problem. The fact I have managed to make it worse suggests to me the loom as it ran same with 2 different MAF sensors. The loom itself is a shambles, I do have a new plug for one end (that I can't find!) but the other end is not great and been soldered a couple of times.

So, does anyone have a spare turbo AFM or an alternative MAF kit gathering dust somewhere?

Thanks in advance

Stuart
 
Well I have found the new plug and have got the loom sorted as best as I can. It made no difference. So I ordered another MAF unit (Bosch HFM - 5) and it also made no difference. A bit of head scratching had me check the vac lines again and noticed that one under the inlet manifold had managed to pop off but it was sitting in such a way that it looked connected, sneaky wee bastard! Popped it in and tie wrapped it secure and instantly my AFR's were back to normal.............. :ROFLMAO:

So off we go for a test run and flooring it in 5th brought on about 24 psi of boost so I quickly backed off! :rolleyes: So today I need to work out what is wrong with that. I replaced the Lindsey WG diaphragm a few years ago, so I'm hoping it isn't that again. I will check the banjo, the lines down to the WG and the MBC. I think I'll dial back the MBC first and see if it makes a difference. Never a dull moment.........
 
I sprayed a tiny squirt of brake cleaner into the hoses and onto the tubes. And fitted small cable ties, seems to help.
 
A visual inspection hasn't highlighted any plumbing issues, however I wound back the MBC a full 4 turns and it has made no difference. So, I have no boost control., well apart from my right foot!

When I'm next at my mates garage I will put an airline down the hoses to see if I have a leak. All the connections look tight and secure, so if its not a control line fault, it must be the actual WG or the MBC. Most likely be the WG diaphragm again, hopefully I'm wrong and it's something stupid and simple!

How can an MBC fail? Could that cause the removal of boost control? I'm pretty sure I have the LR MBC that comes with their WG kit.

Stuart
 
Do you have a bypass valve or a blow-off valve fitted to yours Stuart? I had a slight overboost issue a few years ago which was caused by my Bailey bypass valve sticking. I replaced it with a standard one from Porsche and it fixed the issue.
 
dlknight said:
Do you have a bypass valve or a blow-off valve fitted to yours Stuart? I had a slight overboost issue a few years ago which was caused by my Bailey bypass valve sticking. I replaced it with a standard one from Porsche and it fixed the issue.
Click to expand...

Interesting, I have a Forge re-circ valve that must have been on about 13 years or so. I shall check that out.

I got 18 psi today in 3rd foot to the floor, then also in 4th, then in 5th it shot towards 25 psi. On the next run it shot towards 25 psi in 3rd so I backed off, possibly that valve sticking/unsticking? Would be a cheap fix.

Is there a way to test it?
 
Just looked back on what was happening with mine, unfortunately not the same issue. I took it apart and the valve was getting stuck when compressed which meant that the boost was leaking (so not overboosting). The spring inside should push the valve closed when there is no pressure build-up.

I think you were right with your first assumption, either the wastegate or boost controller acting up.

Clarkes Garage has a wastegate test procedure - https://www.clarks-garage.com/shop-manual/exh-02.htm

Also found this thread on rennlist where they mention that with the wastegate closed you will hit 22+ PSI

Overboosting? What to check? - Rennlist - Porsche Discussion Forums

944 Turbo and Turbo-S Forum - Overboosting? What to check? - Since the weather i much cooler here (yes, it IS cooler here ;) ) i am getting what seem's to be like an overboosting situation. This doesn't always occur, when at WOT and reaching 3,300+rpm, it would hold boost (1.9bar due to test...
rennlist.com
 
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